[Django]-Calling block inside an if condition: django template

You haven’t made a mistake – template blocks are included regardless of any conditionals around them. You can see this from this line of the ExtendsNode class of django/template/loader_tags.py in the Django source code:

self.blocks = {n.name: n for n in nodelist.get_nodes_by_type(BlockNode)]}

When the {% extends %} is being rendered, it fetches all block nodes from the template directly and stores them for rendering when the parent comes across those blocks. Whether those blocks in the child were inside conditionals or not isn’t considered.